The present invention relates to a device for variable actuation of gas exchange valves of internal combustion engines.
Such devices are used to control gas exchange valves in such a way as to make it possible to operate reciprocating engines without the throttle valve that would otherwise be necessary.
Such a device is disclosed in DE 101 23 186 A1, for example. In this device, a rotating cam first drives a connecting link, which executes a pure oscillating rotary motion and carries a radial cam, which is composed of a rest area and a lift area. The radial cam transfers the lifting curve necessary for actuation of the valve to the roller of a driven element similar to a cam follower which in turn actuates the valve. The desired different valve lifting curves are produced by the fact that the center of rotation of the connecting link is displaced on an arc-shaped path which is concentric to the roller of the driven element when it is in the position that it assumes when the valve is closed. The center of rotation is formed by a roller which is provided on the connecting link and which is supported in a non-positive manner on an arc-shaped track in the housing; this track is also concentric to the roller of the driven element, that is, it forms an equidistant to the path of the center of rotation and is designated as the coulisse. In addition, the roller on the connecting link is supported against a cam disk, whose angular position determines the position of the center of rotation on its arc-shaped path.
DE 101 00 173 describes a completely variable valve train which has driving means, for example a cam and, arranged between the driving means and the gas exchange valve, a connecting link, which acts indirectly on the gas exchange valve; the valve stroke can be changed by adjusting an adjustable guide element.
Other devices of this type have been disclosed in which the center of rotation of the connecting link driven by the cam is supposed to be adjusted on a circular path (OS 195 32 334 A1; EP 0 717 174 A1; DE 101 64 493). However, the previous publications do not contain any teaching about how to construct the devices to realize such adjustment.
However, the prior art device has some disadvantages. All known devices have the common disadvantage that due to manufacturing tolerances the more the valve strokes of the individual cylinders are reduced for the purpose of controlling the load, the greater their differences relative to one another. Moreover, the valve strokes of the gas exchange valves of the same cylinder cannot be changed independently. Completely shutting off the gas exchange valves, that is keeping them closed constantly, and the possibility of turning off a cylinder by completely turning off all intake and/or exhaust valves of individual cylinders, has also not previously been known. Another disadvantage results from the fact that the adjustment of the valve lifting curve occurs during the valve stroke of at least individual gas exchange valves. This requires a high adjusting force, that is, a high adjustment torque with high adjusting power.